The present invention relates generally to borescopes and endoscopes, which are well-known optical devices for viewing objects at remote or inaccessible locations. Borescopes and endoscopes usually incorporate means to illuminate the field of view. This typically consists of a bundle of optical fibres for transmitting light from a light source, located externally of the device, through the device and out of an illumination port. The present invention relates to an improved means of providing illumination of the field of view.
Accordingly, the present invention provides an apparatus for use as a borescope or endoscope for viewing an object at a remote or inaccessible location, comprising a tube having a proximal end a distal end, means in the tube for obtaining an image of an object and transmitting it to a viewing device, and illumination means comprising an array of light emitting diodes (LEDs) mounted on a substrate and covered by a common protective shield of optically clear material.
In this way, an external light source and a conventional light guide for transmitting its light to a bundle of optical fibres in the tube is unnecessary. This greatly reduces the light losses, ensuring that more of the light from the light source is available to illuminate the field of view.
In one embodiment, the array of LEDs is positioned at the distal end of the tube adjacent a viewing port provided in the tube.
Alternatively, the illumination means further includes a plurality of optical fibres for transmitting light through the tube from the proximal end to the distal end, wherein the fibres are arranged in annular form and present an annular end face at the proximal end of the tube, wherein the array of LEDs is annular and is positioned at the proximal end of the tube facing the annular end face of the fibres.
In either embodiment, the protective shield may be shaped so as to form a lens to focus light produced by the LEDs.
Alternatively, a separate lens may be positioned in front of the array in order to focus light produced by the light emitting diodes.
If an annular array of light emitting diodes is used, an annular light pipe may be positioned between the array and the end face of the optical fibres for transmitting light from the array to the fibres.
In this case, the distal end of the light pipe may be shaped to form a lens to focus light onto the end face of the fibres.
Alternatively, a separate lens may be positioned between the light pipe and the end face of the optical fibres.
Cooling means may be provided to dissipate any heat produced by the array of LEDs.
The LEDs may emit white light. Alternatively, they may emit blue light, in which case the protective shield preferably incorporates white or yellow phosphor, whereby the array as a whole provides white light.
Alternatively, the array may comprise a plurality of differently coloured LEDs operable in combination to produced white light.
In particular, the array may comprise a mixture of LEDs operable to produce red, green or blue light and means to operate the LEDs so as to provide light which sequentially alternates between red, green and blue.
In further alternative embodiments, the LEDs may produce infra red light or ultraviolet light.
Preferably, the array includes at least fifty LEDs, and more preferably at least eighty LEDs.
If the array is provided at the proximal end of the tube, it may be incorporated in an assembly which is detachable from the tube.